1. Field of the Invention
The present invention relates to a reflective film to be used, for instance, in a reflection type liquid crystal display and for reflecting room light, natural light, etc. on a backside and using this as a light source. In particular, the invention relates to a reflective film having high reflectivity and exhibiting high durability such as anti-oxidation property, and also to a reflection type liquid crystal display using the reflective film and being brighter and easier to look at, and a sputtering target for forming the reflective film.
2. Description of the Related Art
Liquid crystal displays can be classified to a reflection type and a transmission type. The transmission type liquid crystal display must have a lamp as a light source incorporated in it. Because of high power consumption of the lamp, attention is now focused on a reflection type liquid crystal display, which requires no lamp in it and consumes less power.
In the reflection type liquid crystal display, a reflective film is necessarily provided as a reflective (metal) electrode on the backside of a liquid crystal layer of TFT liquid crystal panel or as a reflector on the backside of a transparent electrode of an STN liquid crystal panel. Room light, natural light, etc. are reflected by the reflective film, and it is used as the light source for forming an image. In order to obtain a bright and clear liquid crystal display panel, it is required to increase the reflectivity of the reflective film.
In the past, aluminum thin-film has been used as the reflective film. Aluminum is subject to corrosion due to salt or moisture, and reflectivity is gradually decreased. For this reason, a thin-film mainly comprising Ag is now used.
However, when Ag thin-film is exposed to the air for a long time in the manufacturing process of the liquid crystal display or when it is exposed to a high temperature and high humidity conditions, oxidization of Ag film, Ag grain growth, or coalescence of Ag occurs. This leads to the decrease in reflectivity, and initial high reflectivity of Ag is not sufficiently maintained.